The disclosures of the following priority applications are herein incorporated by reference:
Japanese Patent Application No. 11-270730 filed Sep. 24, 1999;
Japanese Patent Application No. 11-271626 filed Sep. 27, 1999.
1. Field of the Invention
The present invention relates to a flash control device which suitably controls a flash emission amount.
2. Description of the Related Art
With regard to a method for controlling a flash emission device (a strobe) of a single lens reflex camera, in the prior art, a flash control device which controls a flash emission amount has usually been of the TTL flash control type. Further, a type is known in which preliminary light emission is performed before the main light emission during photography and photometry is performed upon the light reflected back from the photographic subject, so as to obtain information for the main light emission.
For example, Japanese Laid-Open Patent Publication No. H3-68928 discloses an automatic light adjustment device which performs photometry by subdividing the light reflected from the photographic subject during preliminary light emission, derives the reflection ratio distribution of the photographic subject based upon this result, and there by obtains information for the main light emission.
Further, there is also a device which determines the light emission amount which is required during the main light emission based upon the results of photometry during the preliminary light emission, and which causes the flash emission section to perform the main light emission using this required emission amount as a target.
However, with the above described prior art flash control device, it sometimes happens that the amount of reflected light during the preliminary light emission falls outside the range over which the flash photometric section can perform photometry because it is too small or is too large, so that the photometric value which is obtained is not sufficiently reliable.
In particular, in the method in which the emission amount for the main light emission at the time of photography is determined in advance based upon the photometric output during the preliminary light emission, it sometimes happens that sufficient exposure accuracy cannot be obtained because the photometric accuracy at the time of the preliminary light emission directly affects the light emission accuracy during the main light emission.
Further, there is a case in which the photometry for the preliminary light emission is performed with TTL on the side of the camera, the direct photometry is performed on the side of the flash unit (the flash device or the strobe unit), and the main emission amount is calculated,at the flash unit based upon the value indicated from the camera and the value of the direct photometry in the flash unit. In this case, since on the side of the camera the photometry is not performed on the beginning of the preliminary light emission to be regarded as warming up of an emission tube, it can happen that the preliminary emission amount which is measured within the camera and the preliminary emission amount which is measured within the flash unit come to differ. In such a case the problem arises that it becomes impossible to calculate an accurate main emission amount for the value indicated from the camera.
The objective of the present invention is to propose a flash control device which can enhance the accuracy of exposure during flash photography by ensuring the photometric accuracy during preliminary light emission, even when the amount of light reflected during preliminary light emission is too small or is too large, and which as a result thereof can accurately calculate the main light emission amount.
Further, the present invention proposes a flash control device which can accurately calculate the main light emission amount, also in the case that the main light emission amount is calculated based upon photometric results for preliminary light emission both on the camera side and also on the flash unit side.
In order to attain the above objective, a flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section on that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; and a flash control section that performs control by, if an output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, resetting a gain related to photometry for the at least one photometric area, and performing again a preliminary light emission by the flash emission section and a preliminary light emission photometry by the flash photometric section.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; and a flash control section that performs control by, if an output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, replacing the output from the at least one photometric area by a predetermined value that is set in advance.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; a main light emission amount calculation section that performs calculation for controlling the main light emission based upon an output of the flash photometric section; and a flash control section that performs control by, if the output from at least one photometric area of the plurality of photometric areas is outside a predetermined range, ensuring that the output from at least one photometric area is not used for calculation by the main light emission amount calculation section.
Another flash control device according to the present invention comprises: a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; a valid area determination section that determines one or more photometric areas to be used for main light emission control based upon an output of the flash photometric section; and a flash control section that performs control by, if outputs from the photometric areas of the flash photometric section that have been determined as valid by the valid area determination section are outside predetermined ranges, performing again a preliminary light emission by the flash emission section and a preliminary light emission photometry by the flash photometric section.
Another flash control device according to the present invention comprises: an ambient light photometric section that divides a photographic field into a plurality of ambient light photometric areas and performs photometry of light intensity of the photographic field due to ambient light; a flash emission section that performs main light emission at photography and preliminary light emission before photography; a flash photometric section that divides a photographic field into a plurality of photometric areas and performs photometry of reflected light from a photographic subject due to the preliminary light emission; and a flash control section that performs control by setting a gain of a flash photometric area of the flash photometric section that corresponds to at least one ambient light photometric area based upon a measured ambient light intensity of the at least one ambient light photometric area of the ambient light photometric section, and then by performing preliminary light emission photometry.
In this flash control device, it is preferred that the flash control section sets the gain of the flash photometric area of the flash photometric section that corresponds to the at least one ambient light photometric area small when the measured ambient light intensity in the at least one ambient light photometric area is great.
Another flash control device according to the present invention comprises: a flash emission section that performs preliminary light emission and main light emission; a flash control section that controls the flash emission section to perform the preliminary light emission and the main light emission; a flash photometric section that performs photometry upon light reflected from a photographic subject during the preliminary light emission; an indication value calculation section that calculates a main light emission amount indication value for calculating a main light emission amount in the flash emission section, based upon an output of the flash photometric section; and a specified information setting section that sets specified information related to a reference emission amount for calculating the main light emission amount in the flash emission section.
In this flash control device, it is preferred that the flash emission section repeats a small light emission of a predetermined emission amount during preliminary light emission. In this case, it is preferred that the specified information setting section, as the specified information related to the reference emission amount, sets a number of invalid small light emissions among small light emissions performed during the preliminary light emission. Furthermore, it is preferred that the specified information setting section sets as invalid a first through a predetermined number of small light emission among small light emissions performed during the preliminary light emission.
Also, it is preferred that the flash control section causes the flash emission section to perform again preliminary light emission when the flash photometric section has failed in preliminary light emission photometry. In this case, it is preferred that the specified information setting section, if preliminary light emission has been performed again, sets small light emissions from a first to end of the first preliminary light emission as invalid.
Also, it is preferred that the specified information setting section sets information showing invalid emission amount during preliminary light emission and information to relate valid preliminary emission amount and main light emission amount.
Also, it is preferred that: the flash emission section is attached to an outside of a main body of the device; a transmission section that transmits the indication value calculated by the indication value calculation section and the specified information set by the specified information setting section to the flash emission section, is further provided; and the flash emission section performs a different type of light emission control that is specified in advance, if the transmission section has failed to transmit information. In this case, it is preferred that the flash emission section performs control according to an external flash light control method, if the main light emission amount cannot be calculated.
Also, it is preferred that the flash emission section performs a different type of light emission control that is specified in advance, when no information has come from the transmission section during a predetermined time period from after an end of preliminary light emission, or when a command arrives for a start of main light emission before information has come from the transmission section. In this case, it is preferred that the flash emission section performs control according to an external flash light control method, if the main light emission amount cannot be calculated.
In the above flash control devices, it is preferred that the flash photometric section performs TTL flash control.
It is preferred that the above flash control devices are used in an electronic still camera that employs an image-capturing element.
Another flash control device according to the present invention comprises: a flash emission section that performs preliminary light emission and main light emission; a first flash photometric section that performs photometry upon light reflected from a photographic subject through a photographic lens of a camera during preliminary light emission; a second flash photometric section that performs photometry directly upon light from the flash emission section during preliminary light emission and during main light emission; a preliminary light emission control section that performs control of preliminary light emission based upon an output of the first flash photometric section; an invalid light emission information generation section that detects invalid light emission during preliminary light emission, and generates information related to the invalid light emission; a main light emission amount indication value calculation section that calculates a main light emission amount indication value for calculating a main light emission amount in the flash emission section, based upon an output of the first flash photometric section obtained excluding the invalid light emission during preliminary light emission; and a main light emission control section that calculates a main light emission amount based upon the main light emission amount indication value, the information related to invalid light emission, and an output of the second flash photometric section obtained during preliminary light emission, and that performs control of main light emission based upon the calculated main light emission amount and an output of the second flash photometric section.
A flash control device in a camera, according to the present invention, comprises: a flash direction section that directs a flash device connected to the camera to perform preliminary light emission and main light emission; a flash photometric section that performs photometry upon light reflected from a photographic subject through a photographic lens of the camera during preliminary light emission; a preliminary light emission control section that performs control of preliminary light emission based upon an output of the flash photometric section; an invalid light emission information generation section that detects invalid light emission during preliminary light emission, and generates information related to the invalid light emission; a indication value calculation section that calculates a main light emission amount indication value for calculating a main light emission amount in the flash device, based upon an output of the flash photometric section obtained excluding the invalid light emission during preliminary light emission; and a main light emission information output section that outputs the main light emission amount indication value and the information related to invalid light emission to the flash device, in order that a main light emission amount can be calculated in the flash device based upon the main light emission on amount indication value, the information related to invalid light emission, and an absolute preliminary light emission amount that was obtained through photometry directly upon light from a flash emission section in the flash device during preliminary light emission.
A flash device connected to a camera, according to the present invention, comprises: a flash emission section that performs preliminary light emission and main light emission based upon a direction from the camera; a flash photometric section that performs photometry directly upon light from the flash emission section during preliminary light emission and during main light emission; a main light emission information input section that inputs, from the camera, information related to invalid light emission during preliminary light emission and a main light emission amount indication value that is calculated based on photometry upon light reflected from a photographic subject through a photographic lens of the camera excluding the invalid light emission during preliminary light emission; a main light emission amount calculation section that calculates a main light emission amount based upon the main light emission amount indication value input by the main light emission information input section, the information related to invalid light emission input by the main light emission information input section, and an absolute preliminary light emission amount that was obtained through photometry by the flash photometric section flash during preliminary light emission; and a main light emission control section that controls a main light emission based upon the main light emission amount calculated by the main light emission amount calculation section and an output of the flash photometric section.